The present invention relates to an overload coupling for protecting drive trains on machines, especially on tractor-drawn agricultural machines, against overload in at least one sense of rotation. The coupling includes a coupling hub, a coupling sleeve and spring-loaded driver cams acting between them.
Overload clutches with spring-loaded driving bodies which engage recesses in the other coupling half of an assembly for the transfer of torque are known (German Pat. No. 10 48 749). Such couplings operate like ratchets. They are generally of simple construction and provide great reliability of operation. A disadvantage in the known ratchet coupling is that, after an overload occurs, and the coupling rotates, a high percussive energy is produced by the spring-loaded pawls seeking to return to their engaged position. This percussive energy produces great wear, heat and mainly also a great amount of noise.
Also, couplings are known in which the driver cams provided for the transfer of torque are turned out of the torque transmitting position when an overload occurs. Such an overload coupling, as described in German Pat. No. 23 27 079, provides that engagement of the coupling in the torque transmitting position can be made only by external intervention. Furthermore, the coupling described therein is of a construction which is not suitable for use in agricultural machines because considerable complexity and expense are involved in the making and providing of the cams and of the mountings with overload protection means associated with each individual cam.
For use in farm machinery, a coupling is required which is simple in operation and requires very little outside intervention to assure its operation. Furthermore, the adjustability provided in the previously known overload coupling is considerably disadvantageous when it is used in agricultural machines. An overload coupling designed for use in farm machinery is to protect the driven equipment and, thus, is especially designed for the driven implement and, therefore, any possible tampering by an untrained person is to be prevented.
Also, in farm machinery construction, overrunning couplings are needed to see to it that the towing of the trailing implement with the drive disengaged has no negative effect on the universal shaft or on the implement drive itself.